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August 9, 2017
Dear Friends of the
Lake;
There has been
significant discussion and questions regarding the recent dead snails that have
been washing up on some of the shores around Forest Lake. We asked the
Comfort Lake Forest Lake Watershed District to investigate.
The majority of snails
washing up onshore are either Chinese Mystery Snails (Cipangopaludina
chinensis) or Banded Mystery Snails (Viviparus georgianus). These are both
invasive species of snails that were introduced to Minnesota via human
activity. They were given the name "Mystery Snails" because for many
years biologists didn't understand their life-cycle and their offspring seemed
to mysteriously appear, fully-formed.
It is common for
mystery snails to display a boom and bust population cycle where they grow
extremely dense, then eat themselves out of their food supply (typically algae
that is scraped from rocks and sometimes filtered from the water) and die back.
It is likely that a massive snail die back is what is causing the snails to
wash up onshore at Forest Lake. These types of large-scale die backs will
continue to occur in Forest Lake's future, but it is hard to predict when.
Almost all of the
snails that I have seen washing up on the shores of Forest Lake are no longer
living. This means that chemical treatment is no longer possible. My suggestion
is that lake residents either leave the dead snails in the lake or gather them
up in a sealed bag and dispose of them in their garbage can.
These species are
considered a Regulated Invasive Species by the Minnesota DNR and cannot legally
be released into public waters (e.g. from an aquarium).
Additional information
about mystery snails can be accessed at the following links:
Minnesota DNR: http://www.dnr.state.mn.us/invasives/aquaticanimals/chinese_banded_mysterysnails/index.html
Sincerely
Jerry Grundtner
Board Member
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